1. Technical Field
The present invention relates to a method for setting up a drive signal in a liquid ejection head.
2. Related Art
In recent years, it has been proposed to employ a liquid ejection head with a plurality of small nozzles in the production of a thin film. A liquid including a functional material is ejected from predetermined nozzles onto a substrate and then fixed to form a thin film.
An example of such a thin film may include an emitting layer for a color filter or an organic electroluminescence panel, or metal wiring.
In a method disclosed in Japanese Unexamined Patent Application, First Publication No. 2003-159787, it is required that a liquid is ejected from a plurality of nozzles in a uniform amount (hereinafter, referred to as “ejection rate”) with no variation for the production of a high quality thin film.
Variation in the ejection rate may cause variation in the amount of the liquid placed on the substrate, which may lower uniformity in the produced thin film.
In a method using a liquid ejection head, for example, a method for manufacturing a color filter using a liquid ejection head, variation in the ejection rate may cause variation in the amount (i.e., the total ejection rate) of the liquid placed on the substrate. As a result, striped density unevenness appears in an obtained color filter.
Such striped density unevenness is easy to visually recognize and thus impairs the quality of the image displayed on the color filter.
A substrate with patterned, sectioned areas is used in the production of a color filter. Such a substrate includes areas between adjacent sectioned areas where no liquid is placed.
In this case, not all the nozzles are used at the same time.
Different models of the color filter may have differently-pitched sectioned areas. Accordingly, ejection patterns should be adjusted in the model.
A large substrate may be scanned several times for placing the liquid, which requires different nozzles for each scanning event.
Such a difference in frequency of use of the nozzles may cause variation in the ejection rate.
Variations in the ejection rate often occur even in a single nozzle if the same drive signal is used for ejection operation. This is because the ejection rate varies in a single nozzle due to differences in the patterns on the substrate or differences in relative positions of the substrate and the liquid ejection head.
In order to address this problem, a technique has been proposed to compensate for the variation in the ejection rate among the nozzles by setting up and supplying drive signals to the nozzles (i.e., drive elements) under several conditions in accordance with gradual changes in the ejection rate. Such a technique is disclosed in, for example, Japanese Unexamined Patent Application, First Publication No. H9-174883.
However, the technique described above requires a determining of a variation in the ejection rate among the nozzles to appropriately set up the conditions (e.g., the voltage level) for the drive signals in order to compensate for (i.e., relatively correct) the variation.
Although it is ideal to set up the drive signals independently for each nozzle, the types (i.e., systems) of the drive signals that can be set up are limited due to a limited hardware configuration or due to limited controls.
Since distribution of the variation in the ejection rate is uneven among nozzle arrays and the heads, it is difficult to set up conditions for the drive signals for each nozzle appropriately in a single process.